Data communication networks may include various computers, servers, nodes, routers, switches, bridges, hubs, proxies, and other network devices coupled to and configured to pass data to one another. These devices will be referred to herein as “network elements.” Data is communicated through the data communication network by passing protocol data units, such as Internet Protocol packets, Ethernet Frames, data cells, segments, or other logical associations of bits/bytes of data, between the network elements by utilizing one or more communication links between the network elements. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network.
The various network elements on the communication network communicate with each other using predefined sets of rules, referred to herein as protocols. Different protocols are used to govern different aspects of the communication, such as how signals should be formed for transmission between network elements, various aspects of what the protocol data units should look like, how protocol data units should be handled or routed through the network by the network elements, and how information such as routing information should be exchanged between the network elements. Ethernet is one such well known networking protocol that has been defined by the Institute of Electrical and Electronics Engineers (IEEE) as standards 802.1 and 802.3.
A routing protocol such as Intermediate System to Intermediate System (IS-IS) may be run on an Ethernet network as described in application Ser. No. 11/537,775, filed Oct. 2, 2006, entitled “Provider Link State Bridging,” (PLSB) the content of which is hereby incorporated herein by reference. In a link state protocol controlled Ethernet network, the bridges forming the mesh network exchange link state advertisements to enable each node to have a synchronized view of the network topology, rather than utilizing a learned network view at each node by using the Spanning Tree Protocol (STP) algorithm combined with transparent bridging. This is achieved via the well understood mechanism of a link state routing system. The bridges in the network have a synchronized view of the network topology, have knowledge of the requisite unicast and multicast connectivity, can compute shortest path connectivity between any pair of bridges in the network, and individually can populate their filtering databases (FDBs) according to the computed view of the network.
An attribute of Ethernet mesh solutions is that multiple forwarding topologies can be virtualized by being assigned a unique VLAN. As described in Ser. No. 11/537,775, when all nodes have computed their role in the synchronized view and populated their FDBs for a given topology, the network will have a loop-free unicast tree to any given bridge from the set of peer bridges; and a both congruent and loop-free point-to-multipoint (p2mp) multicast tree from any given bridge to the same set of peer bridges.
To implement multicast connectivity, nodes on the network advertise interest in multicast service instances. Any node on the shortest path between two nodes advertising common interest in a particular multicast will install forwarding state in the node's filtering database (FDB) for the multicast, so that packet traffic received (directly or indirectly) from any node can be properly forwarded toward the destination node. Although this multicast solution works well, it requires forwarding state to be installed for each multicast source, group pair (S,G). As the number of multicast instances on the network increases, this may require the nodes to install significant forwarding state. Thus, it would be advantageous to allow a routed Ethernet mesh network to be able to utilize less state-intensive tree constructs, with simpler computation requirements, and potentially gain additional mechanisms for the distribution of load on the available network resources.